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KVM: SEV-ES: Use V_TSC_AUX if available instead of RDTSC/MSR_TSC_AUX intercepts 

The TSC_AUX virtualization feature allows AMD SEV-ES guests to securely use
TSC_AUX (auxiliary time stamp counter data) in the RDTSCP and RDPID
instructions. The TSC_AUX value is set using the WRMSR instruction to the
TSC_AUX MSR (0xC0000103). It is read by the RDMSR, RDTSCP and RDPID
instructions. If the read/write of the TSC_AUX MSR is intercepted, then
RDTSCP and RDPID must also be intercepted when TSC_AUX virtualization
is present. However, the RDPID instruction can't be intercepted. This means
that when TSC_AUX virtualization is present, RDTSCP and TSC_AUX MSR
read/write must not be intercepted for SEV-ES (or SEV-SNP) guests.

Signed-off-by: Babu Moger <babu.moger@amd.com>
Message-Id: <165040164424.1399644.13833277687385156344.stgit@bmoger-ubuntu>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Babu Moger 2022-04-19 15:54:44 -05:00 committed by Paolo Bonzini
parent f30903394e
commit 296d5a17e7
4 changed files with 11 additions and 2 deletions
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2
arch/x86/include/asm/cpufeatures.h
View File

@ -405,7 +405,7 @@
#define X86_FEATURE_SEV (19*32+ 1) /* AMD Secure Encrypted Virtualization */
#define X86_FEATURE_VM_PAGE_FLUSH (19*32+ 2) /* "" VM Page Flush MSR is supported */
#define X86_FEATURE_SEV_ES (19*32+ 3) /* AMD Secure Encrypted Virtualization - Encrypted State */
#define X86_FEATURE_V_TSC_AUX (19*32+ 9) /* Virtual TSC_AUX */
#define X86_FEATURE_V_TSC_AUX (19*32+ 9) /* "" Virtual TSC_AUX */
#define X86_FEATURE_SME_COHERENT (19*32+10) /* "" AMD hardware-enforced cache coherency */
/*

8
arch/x86/kvm/svm/sev.c
View File

@ -2926,6 +2926,14 @@ void sev_es_init_vmcb(struct vcpu_svm *svm)
set_msr_interception(vcpu, svm->msrpm, MSR_IA32_LASTBRANCHTOIP, 1, 1);
set_msr_interception(vcpu, svm->msrpm, MSR_IA32_LASTINTFROMIP, 1, 1);
set_msr_interception(vcpu, svm->msrpm, MSR_IA32_LASTINTTOIP, 1, 1);
if (boot_cpu_has(X86_FEATURE_V_TSC_AUX) &&
(guest_cpuid_has(&svm->vcpu, X86_FEATURE_RDTSCP) ||
guest_cpuid_has(&svm->vcpu, X86_FEATURE_RDPID))) {
set_msr_interception(vcpu, svm->msrpm, MSR_TSC_AUX, 1, 1);
if (guest_cpuid_has(&svm->vcpu, X86_FEATURE_RDTSCP))
svm_clr_intercept(svm, INTERCEPT_RDTSCP);
}
}
void sev_es_vcpu_reset(struct vcpu_svm *svm)

1
arch/x86/kvm/svm/svm.c
View File

@ -99,6 +99,7 @@ static const struct svm_direct_access_msrs {
{ .index = MSR_EFER, .always = false },
{ .index = MSR_IA32_CR_PAT, .always = false },
{ .index = MSR_AMD64_SEV_ES_GHCB, .always = true },
{ .index = MSR_TSC_AUX, .always = false },
{ .index = MSR_INVALID, .always = false },
};

2
arch/x86/kvm/svm/svm.h
View File

@ -29,7 +29,7 @@
#define IOPM_SIZE PAGE_SIZE * 3
#define MSRPM_SIZE PAGE_SIZE * 2
#define MAX_DIRECT_ACCESS_MSRS 20
#define MAX_DIRECT_ACCESS_MSRS 21
#define MSRPM_OFFSETS 16
extern u32 msrpm_offsets[MSRPM_OFFSETS] __read_mostly;
extern bool npt_enabled;